Unless otherwise indicated herein, approaches described in this section are not prior art to the claims listed below and are not admitted as prior art by inclusion in this section.
Non-orthogonal multiple access (NOMA) may be a technology beneficial for supporting a massive number of user equipment (UE) requesting intermitting transmissions of small data packets in 5th-Generation (5G) massive machine type communication (mMTC) and two-step random-access channel (RACH) applications. In the 3rd Generation Partnership Project (3GPP) 5G New Radio (NR) study item phase, a variety of NOMA schemes were proposed and discussed, including resource spreading multiple access (RSMA), non-orthogonal coded access (NOCA), interleave division multiple access (IDMA), and interleaved-grid multiple access (IGMA). Certain observations are captured in the 3GPP technical report. The proposed NOMA schemes for uplink (UL) transmissions share the following common features: (1) using multiple access (MA) feature(s) at the transmitter side, and (2) allowing multi-user detector at the receiver side. The proposed NOMA schemes for UL transmissions on a high level follow a basic diagram as that depicted in FIG. 11, including bit-level operations and symbol-level operations.
Under RSMA, multiple UEs are differentiated by scrambling sequences. While this technique allows for simple sequence generation, the performance is relatively poor. Under IDMA, multiple UEs are differentiated by interleave patterns. While this technique allows for better utilization of diversity, a system implementing IDMA would likely be associated with higher complexity. Under IGMA, multiple UEs are differentiated based on different bit-level interleavers, different grid mapping patterns, and different combinations of bit-level interleavers and grid mapping patterns. While this technique allows for more flexibility, a system implementing IGMA would likely be associated with higher complexity.